Need for Non-Invasive Measurement of Bone Quality. Osteoporosis is a major medical problem, with a large percentage of elderly persons being susceptible to non-traumatic fractures (bone fractures sustained from minimum trauma). Bone strength is a primary predictor of bone fractures. Bone strength is determined by both bone density and biomechanical aspects bone quality measurable in the laboratory and, in living organism, by ultrasound.
Currently, bone density can be measured by several methods, including: dual energy x-ray absorptiometry and computer-assisted tomography. From epidemiological studies, bone density is inversely correlated with the rate of skeletal fractures. Thus, bone density has been used to define osteoporosis, with a T-score of less than −2.5 (or below about 75% of normal peak value in the lower spine) referred to as osteoporosis even in the absence of fractures.
Recent discoveries, however, have presented situations in which severe impairment of bone quality can occur. Introduced in 1996, a new class of drugs called “bisphosphonate” has been widely used for the treatment of osteoporosis (Liberman et al., N. Engl. J. Med. 333:1437-1443, 1995). With long-term use, new studies suggest that these drugs can severely impair bone quality, leading to recurrent fractures that do not heal properly (Ott, J. Clin. Endo. Metab. 86:1835, 2001; Odvina, et al., J. Bone Miner. Res., September, 2003; Richer et al., J. Bone Miner. Res., September, 2003; Li et al., Calc. Tissue Intern. 69:281-286, 2001). Moreover, with improvement in surgical techniques and in medical treatments to prevent rejection, more patients are living longer after kidney (renal) transplantation. These patients are known to have increased susceptibility to fractures, since they probably have defective bone from taking steroids and suffer from other factors that are harmful to bone. These clinical conditions presented situations wherein a prominent reduction in bone quality may develop.
Another recent development that emphasizes the need for a reliable method to measure bone quality is the recognition that bone quality, aside from bone density, is an important determinant of fractures in osteoporosis. In 1994, the World Health Organization defined osteoporosis based on bone density alone. In 2000, the NIH Consensus Conference on Osteoporosis defined osteoporosis as “a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture”.
Needed clearly is a device that can measure reliably, quickly and non-invasively the biomechanical quality of bone in vivo. The device should permit for the rapid, accurate, consistent detection of elasticity and strength data. A need also exists for the development of a system that is automated and which has a design, engineering and software for data acquisition that is user-friendly. Finally, a need has arisen for a reliable, inexpensive method for monitoring the status of a patient's bone quality information during treatment of, e.g., osteoporosis or other conditions.